When receiving a strong electromagnetic pulse, electronic equipment cannot operate normally, and in some cases, it is destroyed. EMP (electromagnetic pulse) weapon uses such a phenomenon, in which the strong electromagnetic pulse is generated by any method, and is irradiated to a target to hinder the operation of the electronic equipment or to destroy the electronic equipment.
As a result of the development of the EMP weapon in recent years, it is requested to protect various types of electronic equipment from an attack by such a strong electromagnetic pulse emitted from the EMP weapon. One method for protecting the protection object from the attack by the EMP weapon is a method of covering the whole protection object with a shield formed of an electrically conductive body. However, this method cannot be applied to the protection object such as a radar antenna in which an electric opening is indispensable on the configuration of the apparatus. Also, in a problem of forming the shield, it becomes difficult to prevent the influence of the electromagnetic pulse when a gap is formed in the shield. Also, it is difficult to avoid an adverse influence to the electronic equipment.
From such a background, it is demanded to provide a technique of protecting various protection objects containing a protection object having an electric opening from the attack by the strong electromagnetic pulse.
Note that as the technique in conjunction with the present invention, JP 2007-206588A discloses an aerial visible image forming apparatus that condenses a laser beam to generate plasma, and illustrates a visible image of characters, images and so on the air with visible light outputted from the plasma.